Asian Cardiovasc Thorac Ann 2006;14:371-376
© 2006 Asia Publishing EXchange Ltd
Mitral Valve Surgery for Dilated Cardiomyopathy with Mitral Regurgitation
Masashi Toyama, MD,
Akihiko Usui, MD,
Tomonobu Abe, MD,
Hideki Oshima, MD,
Toshiaki Akita, MD,
Yuichi Ueda, MD
Department of Cardiothoracic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan
For reprint information contact: Masashi Toyama, MD Tel: 81 52 744 2376 Fax: 81 52 744 2383 Email: machapon{at}med.nagoya-u.ac.jp, Department of Cardiothoracic Surgery, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466–8550, Japan.
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ABSTRACT
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Outcomes of surgery for non-ischemic non-valvular dilated cardiomyopathy with associated mitral regurgitation were assessed in 8 consecutive patients who underwent 9 mitral valve operations between 2001 and 2004. Mitral valve replacement was performed when the coaptation depth exceeded 10 mm. Two patients initially underwent mitral valvuloplasty, and 6 underwent valve replacement. One patient had valve replacement soon after valvuloplasty. Transthoracic echocardiography was performed immediately before surgery, before discharge, and during follow-up. Transesophageal echocardiography was carried out intraoperatively to assess valvular and ventricular function. Postoperative mean functional class was significantly better than the preoperative value (2.4 ± 0.7 vs. 3.3 ± 0.7), and the improvement was sustained during follow-up (2.0 ± 0.7). The ejection fraction and left ventricular end-diastolic dimension did not improve. One patient died without leaving hospital and two died during follow-up. The 2- and 4-year survival rates were 75.0% and 37.5%. Mitral valve surgery improved functional class without obvious changes in ejection fraction or left ventricular end-diastolic dimension.
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INTRODUCTION
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Heart transplantation for dilated cardiomyopathy (DCM) has been performed for several decades as a last resort. The transplant rate is falling worldwide because of the shortage of donors, and the results of transplantation are not always satisfactory. Hosenpud and colleagues1 reported that median survival after a heart transplant was 9.8 years. The number of transplants is not increasing in Japan because of donor shortage, religious issues, and the problem of assessing brain death. Several procedures have been proposed as palliatives, including cardiac resynchronization therapy, use of a mesh-like cardiac support device, dynamic cardiomyoplasty, partial left ventriculectomy, mitral valve procedures, ventricular assist devices, and an artificial heart. Mitral regurgitation (MR) is caused by mitral annular dilatation or papillary muscle dysfunction in end-stage cardiomyopathy. Mitral insufficiency sets up a vicious circle, with increasing volume overload leading to annular dilatation and papillary displacement. Mitral regurgitation is a predictor of poor prognosis in patients with DCM.2 We performed simple mitral valve (MV) surgery principally for DCM associated with MR. This study investigates the surgical results and assesses the value of our strategy.
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PATIENTS AND METHODS
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There is no clear definition of DCM. We used the following criteria: ejection fraction (EF) < 40%, and left ventricular end-diastolic dimension (LVDd) > 50 mm.3 Valvular DCM was defined as a valve abnormality caused by a valvular lesion leading to prolapse. Ischemic DCM was defined in patients with coronary stenosis 
75%, or those with an old myocardial infarction. Patients with ischemic, valvular, or congenital DCM were excluded from this study. Eight consecutive patients with DCM associated with MR, who underwent 9 surgical procedures, were enrolled in this study from 2001 to 2004. Written informed consent for the procedures was obtained from all patients. The patient characteristics are listed in Table 1
. Not all patients received maximal medical treatment for congestive heart failure (diuretics, digoxin, angiotensin-converting enzyme inhibitors, beta blockers) because of adverse effects including hypotension.
Transthoracic echocardiography was performed prior to surgery, immediately before discharge from hospital, and during follow-up. Transesophageal echocardiography was performed intraoperatively to assess valvular and ventricular function and morphology. Mitral regurgitation was evaluated by Doppler analysis. Calafiore and colleagues4 defined the mitral coaptation depth as the distance between the mitral annular plane and the coaptation point of the mitral leaflets. They recommended coaptation depth as a helpful parameter in deciding MV surgery. From 2001, we quantified the MV coaptation depth in 7 patients to decide whether mitral valvuloplasty (MVP) or mitral valve replacement (MVR) was feasible. If this parameter exceeded 10 mm, MVR was performed; if it was 
10 mm, MVP was performed. The final decision to repair or replace was made according to the results of intraoperative transesophageal echocardiography. The valve prosthesis was selected according to the ACC/AHA guidelines that recommend mechanical valves for patients with severely impaired left ventricular (LV) function.5 However, a bioprosthesis was chosen if a poor prognosis was expected before surgery. After weaning off bypass, the extent of MR was evaluated. If necessary, bypass was re-instituted to redo the repair or replace the valve.
All patients underwent a median sternotomy and the left atrium was opened through a right lateral left atriotomy. Mitral valve surgery was performed on an arrested heart with blood cardioplegia in 8 procedures on 7 patients. One patient underwent MVR on a beating heart; an aortic crossclamp was applied to prevent air embolism, and the ascending aorta below the clamp site was perfused through the root cannula. This patient needed intubation and intra-aortic balloon pumping (IABP) preoperatively; preoperative echocardiography had revealed LVDd of 70 mm, severe MR, and tricuspid regurgitation. Beating heart surgery was considered to have the important advantages of preserving myocardial perfusion with no reperfusion injury. Initially, 2 patients underwent MVP and 6 had MVR (2 bioprostheses and 4 mechanical valves). In one patient who had undergone MVP, severe MR recurred, and MVR was performed with a mechanical valve 2 months later. The surgical procedures are summarized in Table 2. A Carpentier-Edwards rigid ring and a Physio ring (Edwards Lifescience, Irvine, CA, USA) were used in the 2 patients who had MVP. We aimed to preserve the subvalvular apparatus even with MVR. St. Jude Medical mechanical valves (St. Jude Medical, St. Paul, MN, USA) and Carpentier-Edwards pericardial valves (Edwards Lifescience, Irvine, CA, USA) were implanted for MVR. In most patients, a small triangle of the anterior leaflet was resected and the anterior leaflet was reattached to the fibrous trigone; the posterior leaflet was preserved. The mean cardiopulmonary bypass time was 166.8 ± 35.6 min, and the aortic crossclamp time was 83.4 ± 38.3 min.
Continuous follow-up was maintained by referral cardiologists. Data were obtained from medical records and by interviews with the referring physicians and patients. The mean follow-up was 2.5 ± 1.8 years (range 0.07–4.98 years).
All data were analyzed using SPSS software (SPSS Inc., Chicago, IL, USA). Continuous variables are expressed as mean ± standard deviation. Changes between preoperative and postoperative cardiac function were analyzed by ANOVA. Estimates of survival were calculated using the Kaplan-Meier method.
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RESULTS
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The early results are given in Table 3. Two patients required IABP preoperatively for low output syndrome and continued on this support postoperatively. One patient who needed intubation and IABP preoperatively suffered from liver dysfunction; the total bilirubin and transaminase levels were elevated before surgery. The other, who had been intubated because of heart failure, was extubated before entering our hospital but had an elevated transaminase level and was dependent on IABP for organ perfusion. These two patients required inotropic agents. None of the others needed mechanical ventilation. Cardiac function before and after MV surgery is shown in Table 4 and Figures 1, 2, and 3. Overall, MV surgery improved the functional class without significant changes in EF and LVDd.
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Figure 1. Change in New York Heart Association (NYHA) functional class after mitral valve surgery. *Case no. 2 relapsed into severe mitral regurgitation after mitral valvuloplasty and subsequently underwent mitral valve replacement. Preop = preoperative, Postop = postoperative.
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Figure 2. Change in ejection fraction after mitral valve surgery. *Case no. 2 relapsed into severe mitral regurgitation after mitral valvuloplasty and subsequently underwent mitral valve replacement. Preop = preoperative, Postop = postoperative.
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Figure 3. Change in left ventricular end-diastolic dimension (LVDd) after mitral valve surgery. Preop = preoperative, Postop = postoperative.
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Individual details are listed in Table 5. Patient no. 6, who underwent MVR and cardiac resynchronization therapy, showed improvements in EF and LVDd immediately after the operation. Patients 4, 5, and 7 showed improvements in EF and LVDd in the late phase. In Patients 1 and 3, EF and LVDd did not improve even at the latest follow-up: in no. 1, aortic regurgitation increased from trivial to severe; in no. 3, sarcoidosis was diagnosed pathologically. At the latest follow-up, 4 patients had maintained New York Heart Association (NYHA) functional class I-II, only one (no. 3) was in a worse NYHA class. In patient no. 1 who had undergone MVP, MR relapsed into grade 2 from zero.
The 2 patients who required preoperative IABP support remained in the intensive care unit for 18 days and 25 days; one died in the hospital and the other died of heart failure 30 days after discharge (Table 5
). Her heart failure was triggered by beta-blocker administration. Another patient died of heart failure 4.3 years after surgery although she had been in a stable condition (NYHA class II-III) for 4 years. Survival is illustrated in Figure 4. The 1-year survival was 75% and the 4-year survival was 37.5%.
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DISCUSSION
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Most patients with DCM die from heart failure despite improvements in medical therapy. The 1-year survival was 25% in a study of medically treated patients in NYHA class IV.6 Mitral regurgitation is reportedly an indicator of poor prognosis in patients with DCM. Blondheim and colleagues7 found a signify cantly lower 2-year survival for patients with DCM and MR compared to those without MR. Bolling and colleagues8 performed MVP with an undersized flexible ring in such patients. They reported 1- and 2-year survival of 82% and 72%, NYHA class improved in all cases, and after 24 months of follow-up, all survivors were in NYHA classes I or II. In patients undergoing MV reconstruction alone, they found that reestablishment of a more normal LV mass-to-volume ratio was achieved without losing myocardial mass, compared to LV plasty. In our institution, we performed simple MV surgery for DCM with MR. There was an improvement in NYHA functional class for most patients who were in class III preoperatively. Our results are comparable to those of Bolling and colleagues.8 Hosenpud and colleagues1 reported 1-year survival after cardiac transplantation of 81%, and 4-year survival of approximately 70%. Thus, our results are not as good as those of heart transplantation, but considerably better than the outcome on medical treatment alone.
Preoperative status inevitably affects surgical results. Calafiore and colleagues9 reported that preoperative right ventricular failure, use of inotropes, and IABP were risk factors for poor early survival after surgery. Both of our patients who required IABP preoperatively died in the early phase after surgery. An early operation is indicated before the condition of the patient deteriorates. Proposed prognostic factors include contractile reserve dobutamine echocardiography and type B natriuretic peptide levels.10,11 These could provide important information for deciding the appropriate treatment and the timing of surgery.
Mitral valvuloplasty is the current standard means of correcting MR associated with end-stage cardiomyopathy.2,8 However, MR can reappear in patients treated with ring annuloplasty for ischemic MR; its recurrence is often due to progressive lateral displacement of the papillary muscles and attendant chordal tethering.12 For non-ischemic and non-valvular DCM, the pathologic myocardial change continues after surgery. It could cause further displacement of papillary muscles and recurrence of MR. Calafiore and colleagues4 identified patients in whom MVR was indicated for dilated cardiomyopathy. We were unable to assess the validity of this concept because there were too few cases of MVP in the present study. Earlier operation, before cardiac function deteriorates, might increase the number of MVP procedures. One of the two patients who had undergone MVP relapsed into severe MR. The preoperative EF was only 17%, suggesting that pathologic change was already severe. Echocardiographic data revealed a coaptation depth of more than 1 cm in this case. We believe that this measurement assists decisions of whether to repair or replace the MV.
There are few reports of valve selection criteria in patients with severely impaired LV function, and a mechanical valve has been recommended because of the risk of thromboembolism.5 The optimal valve exerts minimal resistance to forward blood flow, and must have a low incidence of thromboembolism. Factors that predispose to thromboembolic events in patients with congestive heart failure include low cardiac output with relative stasis of blood in dilated cardiac chambers, poor contractility, regional wall motion abnormality, and atrial fibrillation. A high incidence of thromboembolism has been reported in congestive heart failure.13 In contrast, patients with DCM often have chronically low cardiac output that may impair hepatic function. This may predispose to bleeding complications.14 Such patients are at risk of both thromboembolism and hemorrhage. We selected mechanical valve prostheses according to the ACC/AHA guidelines.5 Li and colleagues15 reported that persistent pulmonary hypertension after MVR is associated with prosthesis-patient mismatch. They also suggested that the prosthesis should have the largest effective orifice area for a given size. The new generation bileaflet mechanical valves may be a good option, as their hemodynamics are generally superior to those of other prostheses. Bioprostheses can prevent thromboembolic and bleeding events and do not raise concern over structural valvular deterioration in patients whose prognosis is poor. The MV apparatus should be preserved for ventricular function in DCM, although it might lead to a stuck valve. Bioprostheses with struts also have some advantage in preventing a stuck valve. We believe that a mechanical valve can reduce the pulmonary pressure after MVR, and improve prognosis if the patient’s survival is estimated to be relatively good. We recommend that mechanical valves be used as a rule.
The LVDd and EF did not change significantly postoperatively in our study. In 3 cases, LVDd increased. Schuler and colleagues16 found that patients with chronic MR and a markedly enlarged left ventricle exhibited little change in LVDd after MVR. In those who have suffered severe deterioration, LVDd either does not change or increases because of the invasive procedure. There has been no direct comparison of MV surgery with LV plasty. Bolling and colleagues8 reported that patients who had undergone MVP re-established a more normal LV mass-volume ratio without losing myocardial mass, and this was more frequent in patients with idiopathic DCM than ischemic DCM. Isomura and colleagues17 reported hospital mortality of 14% (11/50) and 3-year survival of 60% after the introduction of echo-guided decision-making for LV plasty in patients with non-ischemic DCM. However, they performed concomitant MV surgery in 89% of patients. Our surgical procedure is much simpler and more effective, with shorter aortic crossclamp and total cardiopulmonary bypass times.
We found reverse remodeling was not achieved in 2 patients: in patient no. 1, severe AR developed; patient no. 3 was diagnosed with DCM caused by sarcoidosis. One patient (no. 6) showed improved cardiac function immediately after MVR followed by cardiac resynchronization therapy. Simple therapies such as cardiac resynchronization and implantation of mesh-like cardiac support devices can independently cause reverse remodeling of the left ventricle.18,19 Olsson and colleagues19 demonstrated that addition of a mesh-like cardiac support device to conventional cardiac surgery improved patient status and reduced LV size in heart failure patients with DCM. Such adjunct therapies to MV surgery can prevent further dilation or lead to earlier reverse remodeling.
Medical therapy has a great impact on long-term survival, as well as on LV geometry and MR. Not all patients underwent maximal medical therapy. There were cases of DCM caused by sarcoidosis or suspected as resulting from chemotherapy with doxorubicin. These would be expected to have a worse survival than those with idiopathic DCM.20 This study has looked at a very small number, without any control group. The most common cause of heart failure is ischemic heart disease. Such an etiology of heart failure, non-ischemic and non-valvular, is very small relative to ischemic heart disease. For greater statistical confidence, a multicenter study in Japan is needed.
Although our surgical results were not wholly satisfactory; when the number of heart transplantations cannot be increased, our simple strategy is reasonable for improving early prognosis. Surgical intervention clearly contributed to the improved outcome in these patients with DCM and MR.
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REFERENCES
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- Bolling SF, Deeb GM, Brunsting LA, Bach DS. Early outcome of mitral valve reconstruction in patients with end-stage cardiomyopathy. J Thorac Cardiovasc Surg 1995;109:676–83.[Abstract/Free Full Text]
- Richardson P, McKenna W, Bristow M, Maisch B, Mautner B, O’Connell J, et al. Report of the 1995 World Health Organization/International Society and Federation of Cardiology Task Force on the Definition and Classification of cardiomyopathies. Circulation 1996;93:841–2.[Free Full Text]
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- Bonow RO, Carabello B, de Leon AC Jr, Edmunds LH Jr, Fedderly BJ, Freed MD, et al. Guidelines for the management of patients with valvular heart disease: executive summary. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Management of Patients with Valvular Heart Disease). Circulation 1998;98:1949–84.[Free Full Text]
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- Blondheim DS, Jacobs LE, Kotler MN, Costacurta GA, Parry WR. Dilated cardiomyopathy with mitral regurgitation: decreased survival despite a low frequency of left ventricular thrombus. Am Heart J 1991;122(3 Pt 1):763–71.[Medline]
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ABSTRACT
INTRODUCTION
